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Characterization of D-tagatose-3-epimerase from Rhodobacter sphaeroides that converts D-fructose into D-psicose
Longtao Zhang1, Wanmeng Mu, Bo Jiang
1State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu, People's Republic of China. zlongtao@hotmail.com
Abstract:
A non-characterized gene, previously proposed as the D-tagatose-3-epimerase gene from Rhodobacter sphaeroides, was cloned and expressed in Escherichia coli. Its molecular mass was estimated to be 64 kDa with two identical subunits. The enzyme specificity was highest with D-fructose and decreased for other substrates in the order: D-tagatose, D-psicose, D-ribulose, D-xylulose and D-sorbose. Its activity was maximal at pH 9 and 40 degrees C while being enhanced by Mn(2+). At pH 9 and 40 degrees C, 118 g D-psicose l(-1) was produced from 700 g D-fructose l(-1) after 3 h.
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